Sulfur hexafluoride (SF6) has been used as a gaseous dielectric (insulator) in electrical equipment since the 1950s. It is now known that SF6 is a potent greenhouse warming gas with one of the highest global warming potentials (GWP) known. The basic physical and chemical properties of SF6, its behavior in various types of gas discharges, and its uses in electrical equipment have been broadly investigated.
Besides its good insulating and heat transfer properties, SF6 has a relatively high pressure when contained at room temperature. It is easily liquefied under pressure at room temperature allowing for compact storage in gas cylinders. However, the liquefaction process can be time consuming, inefficient and relatively expensive.
SF6 has some other undesirable properties: it is an efficient infrared (IR) absorber and due to its chemical inertness, is not rapidly removed from the earth's atmosphere. Both of these properties make SF6 a potent greenhouse gas. The strong infrared absorption of SF6 and its long lifetime in the environment are the reasons for its extremely high global warming potential which for a 100-year time horizon is estimated to be more than 22,000 times greater (per unit mass) than that of CO2, the predominant contributor to the greenhouse effect.
Accordingly, many in the electrical equipment industry have spent substantial time and effort seeking suitable replacement gases to reduce the use of SF6 in electrical equipment. To date, the possible replacement gases have been identified as (i) mixtures of SF6 and nitrogen for which a large amount of research results are available; (ii) gases and mixtures (e.g., low concentrations of SF6 in N2, and SF6—He mixtures) for which a smaller yet significant amount of data is available; and (iii) other potential gases for which little experimental data is available, e.g., Arsenic pentafluoride; Arsine; diboron tetrafluoride; diborane, etc.
These compounds, including SF6, are useful in the gas phase for electrical insulation and for arc quenching and current interruption equipment used in the transmission and distribution of electrical energy. Generally, there are four major types of electrical equipment devices where these gases can be employed for insulation and/or interruption purposes: (1) gas-insulated circuit breakers and current interruption equipment, (2) gas-insulated transmission lines, (3) gas-insulated transformers, and (4) gas-insulated substations. Such gas-insulated equipment is a major component of power transmission and distribution systems all over the world.
Regardless, of which insulation gas is used, including SF6; all of the insulation gases have some amount of global warming potential. When the various types of electrical equipment discussed above require maintenance or when the electrical equipment is used under laboratory or experimental conditions there is a need for an apparatus and method for fast recovery and charge of the insulation gas. Particularly, methods that avoid time consuming and inefficient liquefaction steps. The present invention addresses these problems by avoiding liquefaction of the gas reducing the recovery and charge time of insulation gas from electrical equipment; reducing the cost of maintenance activity; and reducing the amount of escaped gas, thereby reducing the environmental impact of insulation gas recovery and charge in electrical equipment.